60 Hotch
Junior Member
Posts: 9
First Name: Paul
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Post by 60 Hotch on Jun 21, 2024 12:52:24 GMT -5
Hi Rick. I just finished another rebuild on a 636 using a kit from DeBella. When I do a rebuild I completely strip the carb of all the brass and plugs. Then it gets thoroughly washed then glass beaded, then all passages cleaned all threads chased. I reassembled the carb adjust the float to 3/8”, back out the idle speed screw, adjust the pump stroke to 17/32”, then set the high speed needle height without using the gauge making sure that the needle just starts to rise when cracking the throttle per your instructions from a conversation we had a while back when I had a stumbling problem coming off of idle (I’ve been doing this step on all of my rebuilds since). This carb drips from the venturi at idle. I lowered the adjustment for the main needle so it doesn’t raise as soon, still drips. Your thoughts please. Thanks
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Post by Scoutpilot on Jun 21, 2024 15:37:32 GMT -5
Accelerator pump 17/64”
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60 Hotch
Junior Member
Posts: 9
First Name: Paul
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Post by 60 Hotch on Jun 21, 2024 17:24:52 GMT -5
Sorry yes 17/64” my typo
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Post by Scoutpilot on Jun 21, 2024 17:27:13 GMT -5
Is the heat riser working properly?
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60 Hotch
Junior Member
Posts: 9
First Name: Paul
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Post by 60 Hotch on Jun 21, 2024 18:28:55 GMT -5
Yes and I tried 2 known good carbs on the same engine and they worked flawlessly
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Post by Scoutpilot on Jun 22, 2024 4:30:46 GMT -5
Metering rod is not the issue. Reset per usual instructions. I have to ask, the float was set without the gasket in place?
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60 Hotch
Junior Member
Posts: 9
First Name: Paul
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Post by 60 Hotch on Jun 22, 2024 15:42:49 GMT -5
Yes, no gasket installed when adjusting the float. I know you said the metering rod isn’t the problem but I’m gonna lower it to the bottom anyway just for a test
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Post by Scoutpilot on Jun 23, 2024 4:08:55 GMT -5
Adjustment of the metering rod requires holding the rod all of the way down while raising the pin it rests on to a point where it is barely touching the rod eye then tightening the nut while holding it in this configuration.
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60 Hotch
Junior Member
Posts: 9
First Name: Paul
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Post by 60 Hotch on Jun 24, 2024 15:25:21 GMT -5
Afternoon Rick
I lowered the metering rod-no change
I measured the main jet, new-old same size
Swapped and adjusted main jet and rod no change
Measured old and new low speed jet and idle well jet same size
I lowered the float to 7/16 no change
This thing will only run at 3/4 choke. There are no vacuum leaks on the manifold, carb base or anywhere external on the carb.
I’m thinking maybe the body may be at fault
Anymore thoughts?
Thanks
Paul
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Post by Scoutpilot on Jun 24, 2024 18:00:42 GMT -5
The float is supposed to be set at 3/8". Unless you have a rubber-tipped needle. The metering rod is supposed to be bottomed out in the valve. The pin that lifts it is supposed to be touching the top inside of the eye of the rod.
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60 Hotch
Junior Member
Posts: 9
First Name: Paul
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Post by 60 Hotch on Jun 24, 2024 18:26:51 GMT -5
The needle is brass I’m experimenting with a lower float setting. The high speed needle is exactly where you said it should be. I’m running out of ideas.
By the way I purchased 3 rebuilding kits from Pete within about a month of each other. I noticed that the aluminum plugs that come with the kit, should be 1 large 1 medium and 4 small not counting the brass plug. The medium plug was missing in the three kits. They added a 5th small plug. Might want to check your kits. I’m heading over to see him soon and I’m going to mention it to him
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Post by Scoutpilot on Jun 25, 2024 2:56:43 GMT -5
The plug problem is at the manufacturer. I have mentioned it to Pete a few times. It's not his fault when he is forced to order a few thousand of these kits at a time. There are a couple of 539 casting configurations that require the fifth plug.
Take a close look at the float. The tang that contacts the spring-loaded pin in the needle should be smooth as a baby's butt. If you see a depression forming you should buff it out with 800 grit. As well, check the pin that the float pivots on for wear and grooving. A grooved pin can and will alter the float setting during operation. No. None in the kit and I have mentioned that to Pete as well. If you need one, I can send it to you. Look to the holes where the pin connects the float to the bowl cover for elongation by wear. That too can alter the float setting during operation.
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60 Hotch
Junior Member
Posts: 9
First Name: Paul
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Post by 60 Hotch on Jul 3, 2024 19:34:16 GMT -5
The float is perfect in every way so is the cover where the float mounts. Not that this makes a deference but is there a spec on float drop? I’ll tell Pete anyway, were paying enough for these kits. My next experiment is switch switch float bowls
I have a Joe’s Motor Pool WO on the bench now that I’m checking for a friend. It went sour last week and had been working pretty well for the last year. The jets are slightly under sized but that’s all I could find short very minor silt in the bowl (that’s all you need for trouble). The carb was very nicely cast and machined, a bit too smooth though for a reproduction. Lets see how it turns out I’ll keep you posted on that one. Have a great day!
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Post by Scoutpilot on Jul 4, 2024 2:29:41 GMT -5
"Silt in the bowl"? How about filtration? What are you doing for that?
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oilleaker1
Full Professor
Full Professor
Has Jeep Disease
Posts: 2,022
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Post by oilleaker1 on Jul 4, 2024 6:34:59 GMT -5
Fuel dripping brings to mind one of my M38's. I went crazy trying new parts until a friend said to check for a very tiny crack in the float bowl. Sure enough, it had one you really couldn't see unless under magnification.
3/4 choke still means you have a vacuum/air leak somewhere.
Valves set to the correct clearance
throttle body shaft leaking/worn
base gasket/insulator staples or copper rivet holding the base up a bit. (you need to pre-crush the copper rivet) or add another thin gasket top and bottom.
cracked intake manifold
alignment of intake/exhaust flanges off and leaking past gasket
Slow speed idle jet plugged or the slow speed idle jet threaded caps leaking past . (Had this a couple of times out on the trail) The dirt in the float bowl bottom can cause this too.
Testing for a vacuum leak with propane or carb clean does not always show a leak either.
The number one cause for no idle has usually been the base gasket is leaking.
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